In the manufacturing of semiconductor elements and so on, treatment such as etching is performed on the surfaces of semiconductor wafers by supplying reactant gas into vacuum containers (that is, at a predetermined degree of vacuum). In order to improve quality, it is necessary to precisely control pressures in the vacuum containers.
In such semiconductor production equipment of the prior art, a massflow meter is provided on a gas supply tube for supplying gas into a vacuum container, and a variable conductance valve is provided on a gas discharge tube for discharging gas from the vacuum container. The valve is controlled such that a pressure from a pressure meter provided on the vacuum container reaches a target pressure (e.g., see Japanese Patent Laid-Open No. 62-47719).